Preloved is a bit of a sore subject, there are a few good advertisers on there (such as you would be if you chose it) but it does have a reputation for being a dumping ground and to be totally honest, many serious goat keepers avoid it now which is really sad for people who are selling lovely, healthy well rounded goats.
There is a FB group which is a sideshoot from 'goaty friends' its called goats for sale uk i think? or BGS if they are registered, best bet.